1. Field of the Invention
The present invention relates to a drive power transmission apparatus for transmitting a drive power from a drive power source to a first rotating means incorporated in a rotation-receiving unit via a second rotating means incorporated in a drive power source by operatively connecting the first and second rotating means. More specifically, the present invention relates to a drive power transmission apparatus capable of suspending an operative interconnection between the first and second rotating means when an excessively high reactive load torque is produced by the rotation-receiving unit due to some trouble in the rotation-receiving unit, so that any adverse affect on the drive power source due to the excessively high reactive load may be prevented. The present invention is preferably but non-exclusively applicable to a power transmission apparatus for transmitting a drive power from a vehicle engine to a clutchless-type or a clutch-incorporating-type refrigerant compressor.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 8-159028 discloses a typical conventional power transmission apparatus incorporated between, for example, a vehicle engine and a refrigerant compressor. The conventional power transmission apparatus has a plurality of rolling balls interposed between a pulley operatively connected to a drive power source (the vehicle engine) by a belt, and a rotated member formed as a hub-like plate fixed to a rotatable power transmitting shaft (a drive shaft of the refrigerant compressor) incorporated in a drive power receiving unit (the refrigerant compressor). In the normal operating state, the plurality of rolling balls are received in both ball receiving recesses formed in the rotated member and ball retaining recesses formed in the pulley, respectively. The pulley and an angular bearing unit mounted on the housing of the compressor are elastically urged toward the rotated member by a preloading spring, such as a disk spring. The rotation of the pulley is transmitted through the rolling balls and the rotated member to the rotatable shaft. In this power transmission apparatus, the rolling balls are forced to move out of the retaining recesses to interrupt power transmission from the pulley to the rotated member when a load torque produced by the rotation receiving unit, i.e., a refrigerant compressor is excessively large.
In the conventional power transmission apparatus, the rolling balls are arranged in a peripheral part of the rotated hub-like plate, and therefore, the rolling balls are subject to the effect of centrifugal force when the rotated hub-like plate member rotates together with the pulley. Accordingly, the rolling balls might be forced to move out of the ball receiving recesses of the rotated hub-like plate and the ball retaining recesses of the pulley by centrifugal force. Namely, the transmission of a drive power might be unintentionally interrupted even if a load torque produced by the rotation receiving unit is not excessively large.